This number is a prime.
The smallest prime of the form 10p - p, where p is prime. [Luhn]
The Schleicher K7 is a vintage two-seat glider with three axis controls which would remain airborne for approximately five minutes off a 997-foot winch launch in still air. [Croll]
"Nine hundred and ninety-seven" is the largest oban (short for " 'o' banned ") prime since primes beyond it use the word "thousand(s)" and/or the suffix "-illion(s)" in their names. [Beedassy]
The sum of digits of the largest 3-digit prime (997) provides the number of primes less than or equal to the largest 2-digit prime. This is not true for any other tier of n-digit numbers. [Green]
The smallest prime whose sum of digits is an odd composite number. [Loungrides]